A CMOS power amplifier with an adaptive bias scheme for mobile radio frequency identification reader applications

,substrate and ground plane, reducing the contact voltage about 2 V in the simulations. Fig. 3 shows the displacement as a function of the beam height. This displacement is independent of the beam height when fringing effects are neglected. However, when beam height decreases, the fringing capacitance increases resulting in an increase of the force and displacement for a given applied voltage. This result demonstrates again that to take into consideration fringing fields is essential in these structures. Finally, Fig. 4 shows the simulated force at the contact with and without the inclusion of fringing effects. This figure shows that fringing effects increase the capacitance and the force. This fact improves the contact reducing its resistance and the switch losses. The measured performance of the manufactured device is shown in Fig. 5, along with its photograph [5]. Insertion loss is 0.13/0.41 dB at 0.9/6 GHz, return loss is 37.7/28.7 dB at 0.9/6 GHz and isolation is 60.2/31 dB at 0.9/6 GHz. These results are comparable to the ones obtained in [4] on a highresistivity silicon substrate. 4. CONCLUSIONS A model for prediction of the actuator displacement in electrostatically actuated, lateral contact RF MEMS series switches has been presented, a switch topology with increasing acceptance due to the evolution of thick metal layers technology. It has been demonstrated that in this topology the parallel-plate approximation for actuator displacement can not be assumed. In addition, it has also been demonstrated the importance of considering fringing fields in the model for a reliable prediction. The simulated results match very well with the measured actuation characteristics of a series switch with electrostatic interdigital actuation manufactured with MetalMumps TM .